THE STATIC AND DYNAMIC STRUCTURE FACTOR OF EXPANDED LIQUID ALKALI METALS

Abstract
We present results from neutron diffraction experiments on liquid rubidium and cesium from their melting point up to their liquid-vapour critical point. Near their critical point, the change from a liquid metal to a nonmetal takes place. The characteristic changes of the electronic properties and of the microscopic structure, such as the mean distance and number of nearest neighbours, which occur during the expansion of the liquid metals, are discussed. By inelastic neutron scattering, also the coherent dynamic structure factor S(Q,ω) of expanded liquid rubidium has been measured up to 1700 K at conditions close to the liquid-vapour coexistence curve. The existence of collective density excitations at short wavelength and high frequency for the expanded liquid metal is discussed and the Enskog self-diffusion coefficient is evaluated from the experimental data.